Electrodes for the electrical contacting of microacoustic components are known from the prior art. For example, German publication 102 06 369 A1 discloses an electrode structure with improved power compatibility and a method for the production thereof. This reference proposes for a component operating with acoustic waves to arrange the electrode structure over a mechanically stable adaptation layer, which serves for reducing the electromechanical stress.
In general, when selecting electrode materials for microacoustic components, their mechanical, acoustic and electrical properties must be weighed up, in particular their acoustic impedance and electrical conductivity. As a consequence, sometimes layer systems of different metals or metal alloys are used for the electrical contacting of microacoustic components instead of a homogeneous layer. Such multilayered electrode structures are also referred to as sandwich structures.
In particular in the production of microacoustic components, the individual, relatively thin layers are produced by methods known from the area of semiconductor fabrication, such as in particular sputtering or vapor deposition. Further process steps comprise what is known as annealing, which is used, inter alia, to compensate for structural defects by heating the structures which have grown.
Tests have shown that these and further process steps influence the properties of the sandwich structures produced in this way, for example, their conductivity. The action of electrical fields may also have adverse effects on the sandwich structures. In particular, the combined conductivity of such sandwich structures decreases again during the depositing of further layers and also during subsequent processing steps, such as, for example, the annealing of the microacoustic component.